BACKGROUND: B cells of patients with common variable immunodeficiency (CVID) disorders display impairment in production of immunoglobulin class-switched antibodies, which is possibly contributed to by defects in early B-cell activation. On resting B cells, B-cell receptors (BCRs) are organized in oligomers that are signaling inactive. Their triggering by cognate antigen causes the lateral reorganization of BCRs and associated proteins into signalosomes, resulting in BCR-activated calcium entry. In resting cells the B-cell surface antigen CD20 is associated with the BCR but dissociates on signalosome formation. OBJECTIVE: We sought to determine whether CD20 dissociation from the BCR during early B-cell activation might contribute to the development of CVID disorders. METHODS: We evaluated BCR signalosome formation, internalization, and signaling in primary B cells of pediatric patients with CVID disorders and healthy control subjects. RESULTS: In many pediatric patients with CVID disorders, B cells exhibit significant deficits in BCR triggering-mediated calcium entry in the cytosol, which correlates with impaired plasmablast differentiation in vitro. These alterations did not originate from upregulation of CD22 or defects in calcium channels and did not involve gene mutations in phospholipase Cγ2 or Bruton tyrosine kinase. Instead, B cells from patients with CVID disorders exhibited reduced BCR dissociation from CD20. BCR or CD20 cross-linking induced less BCR internalization, and antibody-mediated CD20 triggering elicited less BCR downstream signaling, as measured based on secondary fluxes. CONCLUSIONS: We propose that CD20 dissociation from the BCR signalosome is pivotal to BCR-mediated calcium mobilization in the cytosol. Defects in CD20/BCR signalosome conformation might predispose to the spectrum of CVID disorders.
BACKGROUND: B cells of patients with common variable immunodeficiency (CVID) disorders display impairment in production of immunoglobulin class-switched antibodies, which is possibly contributed to by defects in early B-cell activation. On resting B cells, B-cell receptors (BCRs) are organized in oligomers that are signaling inactive. Their triggering by cognate antigen causes the lateral reorganization of BCRs and associated proteins into signalosomes, resulting in BCR-activated calcium entry. In resting cells the B-cell surface antigen CD20 is associated with the BCR but dissociates on signalosome formation. OBJECTIVE: We sought to determine whether CD20 dissociation from the BCR during early B-cell activation might contribute to the development of CVID disorders. METHODS: We evaluated BCR signalosome formation, internalization, and signaling in primary B cells of pediatric patients with CVID disorders and healthy control subjects. RESULTS: In many pediatric patients with CVID disorders, B cells exhibit significant deficits in BCR triggering-mediated calcium entry in the cytosol, which correlates with impaired plasmablast differentiation in vitro. These alterations did not originate from upregulation of CD22 or defects in calcium channels and did not involve gene mutations in phospholipase Cγ2 or Bruton tyrosine kinase. Instead, B cells from patients with CVID disorders exhibited reduced BCR dissociation from CD20. BCR or CD20 cross-linking induced less BCR internalization, and antibody-mediated CD20 triggering elicited less BCR downstream signaling, as measured based on secondary fluxes. CONCLUSIONS: We propose that CD20 dissociation from the BCR signalosome is pivotal to BCR-mediated calcium mobilization in the cytosol. Defects in CD20/BCR signalosome conformation might predispose to the spectrum of CVID disorders.
Authors: Ewoud B Compeer; Willemijn Janssen; Annet van Royen-Kerkhof; Marielle van Gijn; Joris M van Montfrans; Marianne Boes Journal: Oncotarget Date: 2015-05-10
Authors: Michael B Fischer; Wendelin Wolfram; Christoph J Binder; Georg A Böhmig; Markus Wahrmann; Martha M Eibl; Hermann M Wolf Journal: Front Immunol Date: 2015-05-06 Impact factor: 7.561
Authors: Barbara Piątosa; Małgorzata Pac; Katarzyna Siewiera; Barbara Pietrucha; Maja Klaudel-Dreszler; Edyta Heropolitańska-Pliszka; Beata Wolska-Kuśnierz; Hanna Dmeńska; Hanna Gregorek; Irena Sokolnicka; Aneta Rękawek; Katarzyna Tkaczyk; Ewa Bernatowska Journal: J Clin Immunol Date: 2013-02-07 Impact factor: 8.317